Study of acidic degradation of alkali-activated materials using synthetic C-(N)-A-S-H and N-A-S-H gels

Wang, Yanru and Cao, Yubin and Zhang, Zuhua and Huang, Jizhong and Zhang, Peng and Ma, Yuwei and Wang, Hao (2022) Study of acidic degradation of alkali-activated materials using synthetic C-(N)-A-S-H and N-A-S-H gels. Composites Part B: Engineering, 230:109510. pp. 1-14. ISSN 1359-8368

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Abstract

Alkali-activated materials (AAMs) are usually recognized having better acid resistance compared to ordinary Portland cement (OPC), however, the detailed mechanism has not been well studied due to the complexity of raw materials and hardened matrix. In this study, two typical binding gels in AAMs, sodium aluminum silicate hydrate (N-A-S-H) and calcium (sodium) aluminum silicate hydrate (C-(N)-A-S-H), were chemically prepared by laboratory synthesized aluminosilicate powders. The microstructure and composition evolution of the two gels exposed to sulfuric acid were investigated. The results showed that the C-(N)-A-S-H gel had higher degree of structural order than the N-A-S-H gel, while the N-A-S-H gel showed higher polymerization. The AlIV in N-A-S-H gel transferred completely to AlV during sulfuric acid attack, while trace amount of AlIV was still detected in the exposed C-(N)-A-S-H gels. Both gels had increased silica polymerization degree after exposure to sulfuric acid solution. Due to rapider dealumination of N-A-S-H gel than C-(N)-A-S-H gel, the Si/Al ratio increased much higher in the former. The molecular framework changes of N-A-S-H gel caused by dealumination was found to have less effect on the integrity though than that of C-(N)-A-S-H gel, in which coarse gypsum crystalline grains formed and led to destructive stress in hardened matrix. This paper provides an insight at microstructure level of the two typical gels, which is essential for the manufacturing and application of alkali-activated materials.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Faculty/School / Institute/Centre: Current - Institute for Advanced Engineering and Space Sciences - Centre for Future Materials (1 Jan 2017 -)
Faculty/School / Institute/Centre: Current - Institute for Advanced Engineering and Space Sciences - Centre for Future Materials (1 Jan 2017 -)
Date Deposited: 17 Jan 2022 22:52
Last Modified: 17 Jan 2022 22:52
Uncontrolled Keywords: Acid resistance; Alkali-activated materials; Aluminosilicates; C-(N)-A-S-H; Durability; N-A-S-H
Fields of Research (2008): 09 Engineering > 0905 Civil Engineering > 090503 Construction Materials
Fields of Research (2020): 40 ENGINEERING > 4005 Civil engineering > 400505 Construction materials
Socio-Economic Objectives (2008): D Environment > 96 Environment > 9699 Other Environment > 969999 Environment not elsewhere classified
Socio-Economic Objectives (2020): 18 ENVIRONMENTAL MANAGEMENT > 1899 Other environmental management > 189999 Other environmental management not elsewhere classified
Identification Number or DOI: https://doi.org/10.1016/j.compositesb.2021.109510
URI: http://eprints.usq.edu.au/id/eprint/45498

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